There is a considerable need for small, inexpensive yet highly efficient valves, adapted to function as pressure relief valves, vacuum relief valves or check valves, to prevent reverse fluid flow. For example, there are many applications for such valves in the medical field. Specifically, such valves are employed in intravenous fluid supply systems.
In many applications, it is necessary that the valve have a low cracking pressure, in that the valve will be operated between its closed and open positions by a low pressure differential. For such applications, certain disc-type valves have been produced, in which the movable valve member is in the form of a thin disc. However, problems have been encountered with such disc-type valves, in that they have been difficult to assemble and somewhat unreliable in operation. The assembly difficulties have led to high reject rates in that a rather high percentage of the assembled valves has been defective, so that it has been necessary to discard the defective valves.